JP6079869B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

Since silicon oxide represented by silicon (Si) and SiO _x has a higher capacity per unit volume than carbon materials such as graphite, application to a negative electrode active material is being studied. In particular, SiO _x is expected to be put to practical use at an early stage because the volume expansion coefficient when Li ⁺ is occluded during charging is smaller than that of Si. For example, Patent Document 1 proposes a nonaqueous electrolyte secondary battery in which SiO _x is mixed with graphite to form a negative electrode active material.

JP2011-233245A

However, the non-aqueous electrolyte secondary battery using SiO _x or the like as the negative electrode active material has a problem that the cycle characteristics are significantly lowered as compared with the case where graphite is used as the negative electrode active material.

The main causes of the above problems are that the volume change of SiO _{x and the} like during charging and discharging is larger than that of graphite, and the increase in irreversible capacity due to the reaction between SiO _x and the electrolytic solution.

In order to solve the above problems, a non-aqueous electrolyte secondary battery according to the present invention includes a negative electrode active material containing a material represented by SiO _x (0 <x <2), and the value of x in the general formula is X _{s on} the surface and x _{b in the} center, where x _b <x _s and the depth of the substance from the surface where x = (x _s + x _b ) / 2 is _expressed as z _a (μm), When the average particle diameter of the substance is R (μm), 0.05 <z _a , 0.025 ≦ z _a /R≦0.4 , and R ≦ 30 .

According to the present invention, cycle characteristics can be improved in a nonaqueous electrolyte secondary battery using SiO _x as a negative electrode active material.

It is an electron microscope image which shows the cross section of the negative electrode active material particle (after 25 cycles) used in Experiment 4.

  Hereinafter, embodiments of the present invention will be described in detail. In this specification, “substantially **” is intended to include not only exactly the same, but also those that are recognized as substantially the same, with “substantially equivalent” as an example.

  A nonaqueous electrolyte secondary battery which is an example of an embodiment of the present invention includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a nonaqueous electrolyte including a nonaqueous solvent. A separator is preferably provided between the positive electrode and the negative electrode. As an example of the non-aqueous electrolyte secondary battery, there is a structure in which an electrode body in which a positive electrode and a negative electrode are wound via a separator and a non-aqueous electrolyte are housed in an exterior body.

[Positive electrode]
The positive electrode is preferably composed of a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. For the positive electrode current collector, for example, a conductive thin film, particularly a metal foil or alloy foil that is stable in the potential range of the positive electrode such as aluminum, or a film having a metal surface layer such as aluminum is used. The positive electrode active material layer preferably contains a conductive material and a binder in addition to the positive electrode active material.

  The positive electrode active material is not particularly limited, but is preferably a lithium-containing transition metal oxide. The lithium-containing transition metal oxide may contain non-transition metal elements such as Mg and Al. Specific examples include lithium-containing transition metal oxides such as lithium cobaltate, olivine lithium phosphate represented by lithium iron phosphate, Ni—Co—Mn, Ni—Mn—Al, and Ni—Co—Al. It is done. These positive electrode active materials may be used alone or in combination of two or more.

  As the conductive material, carbon materials such as carbon black, acetylene black, ketjen black, graphite, and a mixture of two or more of these can be used. As the binder, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, and a mixture of two or more thereof can be used.

[Negative electrode]
The negative electrode preferably includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. For the negative electrode current collector, for example, a conductive thin film, particularly a metal foil or alloy foil that is stable in the potential range of the negative electrode such as copper, or a film having a metal surface layer such as copper is used. The negative electrode active material layer preferably contains a binder in addition to the negative electrode active material. As the binder, polytetrafluoroethylene or the like can be used as in the case of the positive electrode, but styrene-butadiene rubber (SBR), polyimide, or the like is preferably used. The binder may be used in combination with a thickener such as carboxymethylcellulose.

Silicon oxide (SiO _x ) is used for the negative electrode active material. SiO _x (0 <x <2) has, for example, a structure in which Si is dispersed in an amorphous SiO ₂ matrix. As the negative electrode active material, SiO _x may be used alone, but from the viewpoint of achieving both high capacity and improved cycle characteristics, the volume change due to charge / discharge is mixed with other negative electrode active materials smaller than SiO _x and used. Is preferred. Other negative electrode active materials whose volume change due to charge / discharge is smaller than that of SiO _x are not particularly limited, but are preferably carbon-based active materials such as graphite and hard carbon.

When SiO _x is used in combination with another negative electrode active material whose volume change due to charge / discharge is smaller than that of SiO _x , for example, when SiO _x is used in combination with graphite, the ratio of SiO _x to graphite is A ratio of 1:99 to 20:80 is preferred. If the mass ratio is within the range, it is easy to achieve both higher capacity and improved cycle characteristics. On the other hand, when the ratio of SiO _{x to} the total mass of the negative electrode active material is lower than 1% by mass, the merit of increasing the capacity by adding SiO _x is reduced.

The silicon oxide is represented by the general formula SiO _x (0 <x <2). When the value of x in the above formula is x _s at the surface and x _b at the center, x _b <x _s . , if the _{SiO x x = (x s +} x b) / 2 and becomes a depth from the surface _{z a (μm),} an average particle diameter of SiO _x was _{R (μm), 0.05 <z} a, 0.025 ≦ z _a /R≦0.4.

That the value of x of SiO _x satisfies x _b <x _s means that the oxygen concentration at the surface is higher than the central portion of SiO _x . Further, it is 0.05 <z _a, depth from the surface of the high oxygen concentration layer means that greater than 0.05 .mu.m.

z _a / R is more preferably 0.05 to 0.3. When z a _{/ R} is small, i.e., depth from the surface of the high oxygen concentration layer is too small for the particle size of the SiO _x, tends to react easily occurs between the SiO _x and the electrolyte . When z a _{/ R} is large, i.e., when the depth from the surface of the high oxygen concentration layer is too large for the particle diameter of SiO _x, capacity reduction of the active material due to oxidation of Si in SiO _x is likely to occur Tend to be.

The z _a is more preferably from 0.1 to 20 μm, more preferably from 0.25 to 10 μm, and further preferably from 0.5 to 5.0 μm. If z _a is too small, the reaction between Si in SiO _x and the electrolytic solution tends to occur. When z _a is too large, the capacity of the active material in SiO _x tends to decrease.

The surface of the SiO _x, when incorporating SiO _x battery, means a portion in contact with the electrolyte. The center part of SiO _x is a part that does not come into contact with the electrolyte in the battery and means the center of gravity of the particles.

_{X s} of the surface of the SiO _x means a value of the portion from the outermost surface of the SiO _x to a depth of 30nm towards the center. The _{x b} of the central portion of the SiO _x, refers to a value at a portion where the value of x in SiO _x is a constant value inside the particles.

Examples of the case where the oxygen concentration of SiO _x continuously decreases from the surface of the particle toward the inside, or a case where the oxygen concentration is clearly divided into a surface layer having a high oxygen concentration and a central portion having a low oxygen concentration are exemplified. When the oxygen concentration of SiO _x is divided into a surface layer having a high oxygen concentration and a central portion having a low oxygen concentration, the oxygen concentration continuously decreases from the surface toward the inside in the surface layer and / or the central portion. It is also included. When the oxygen concentration of SiO _x continuously decreases from the surface of the particle toward the inside, for example, when an SEM reflected electron image of the particle cross section is observed, the oxygen concentration is continuously increased from the dark particle surface toward the bright center. The brightness has changed. When the oxygen concentration of SiO _x is divided into a surface layer having a high oxygen concentration and a central portion having a low oxygen concentration, for example, when an SEM reflected electron image of the particle cross section is observed, the contrast between the dark surface portion and the bright central portion is observed. Is different.

When the oxygen concentration of SiO _x is divided into a surface layer with a high oxygen concentration and a central portion with a low oxygen concentration, from the outermost surface of SiO _x to the boundary between the surface layer with a high oxygen concentration and the central portion with a low oxygen concentration Is approximately equal to z _a .

The relationship between the depth (z) from the surface and the oxygen concentration (x) of the SiO _x particles can be determined using secondary ion mass spectrometry (SIMS) and high frequency inductively coupled plasma (ICP). . The oxygen concentration of bulk SiO _x can be specified by ICP, and a certain thickness is removed from the surface by ion etching with SIMS, and the operation of analyzing Si and O on the remaining surface is repeated, whereby z And x can be obtained. In addition to the above, the relationship between the depth (z) from the surface of the SiO _x particle and the oxygen concentration (x) is obtained by cutting the particle by an ion milling method and analyzing the composition of the cross section of the particle using EDS or the like. It is possible. The oxygen concentration (x) can be calculated from the O / Si intensity ratio of the particle surface and the central part.

The average particle size of SiO _x is preferably 1 to 30 μm, more preferably 1 to 20 μm, and even more preferably 2 to 15 μm. In the present specification, the “average particle diameter” means a particle diameter (volume average particle diameter; D ₅₀ ) at which the volume integrated value becomes 50% in the particle size distribution measured by the laser diffraction scattering method. Dv ₅₀ can be measured, for example, using “LA-750” manufactured by HORIBA. When the average particle size of SiO _x is small, the particle surface area increases, so that the amount of reaction with the electrolyte increases and the capacity tends to decrease. On the other hand, when the average particle size is large, the volume change amount due to charge / discharge tends to increase.

The surface of SiO _x is preferably covered with an electron conductive material. The electron conductive material is made of a material having higher conductivity than SiO _x . The electroconductive material is preferably electrochemically stable, and is preferably at least one selected from the group consisting of carbon materials, metals, and metal compounds.

  Examples of the carbon material include carbon black, acetylene black, ketjen black, graphite, and a mixture of two or more thereof. As the metal, Cu, Ni, and alloys thereof that are stable in the negative electrode can be used. Examples of the metal compound include a Cu compound and a Ni compound.

The coverage of the electronic conductive material on the surface of SiO _x is less than 100%, more preferably 5 to 80%. That is, it is preferable that the surface of SiO _x is exposed. When the coverage is small, the conductivity between SiO _x particles tends to be low. When the coverage is large, that is, when the coverage of the electronic conductive material is 100%, a side reaction product due to the reaction between the electronic conductive material and the electrolytic solution is generated and tends to be easily deposited on the particles. is there.

The electronic conductive material is preferably attached to the surface of SiO _x .

The average thickness of the electron conductive material covering the surface of the SiO _x, taking into account the Li ⁺ diffusion properties to the conductive secure and SiO _x or the like is preferably 1 to 200 nm, 5 to 100 nm is more preferable.

As a method for coating the surface of SiO _{x with} an electronic conductive material, for example, a CVD method, a sputtering method, an electrolytic plating method, an electroless plating method, a coal pitch method, or the like can be used. For example, when a coating made of a carbon material is formed on the surface of SiO _x particles by a CVD method, the SiO _x particles and a hydrocarbon-based gas are heated in a gas phase, and carbon generated by thermal decomposition of the hydrocarbon-based gas is removed. Deposit on SiO _x particles. As the hydrocarbon gas, methane gas or acetylene gas can be used.

It is preferable that the region from the surface of SiO _x to z _{a comprises a} lithium silicate phase. When the oxygen concentration on the surface of SiO _x is high, Si in the SiO _x easily reacts with the electrolytic solution, thereby forming a lithium silicate phase. When the region from the surface of SiO _x to z _a has a lithium silicate phase, the subsequent reaction between SiO _x and the electrolytic solution is suppressed. Examples of the lithium silicate include Li ₄ SiO ₄ , Li ₂ SiO ₃ , Li ₂ Si ₂ O ₅ , and Li ₈ SiO ₆ .

When a negative electrode active material containing a material represented by SiO _x (0 <x <2) is provided and the value of x in the general formula is x _s at the surface and x _b at the center, x _b <x a _{s, x} in the material _{= (x s + x b)} / 2 and becomes a depth from the surface _{z a (μm),} if the average particle size of the material was R (μm), 0.05 < SiO _x satisfying z _a and 0.025 ≦ z _a /R≦0.4 can be obtained, for example, by the following method. A negative electrode active material containing a substance represented by the general formula SiO _x (0 <x <2) is provided, 5% to 80% of the surface of the substance is covered with an electronic conductive material, and the electronic conductive material is The nonaqueous electrolyte secondary battery adhering to the surface of the substance is charged and discharged for 25 cycles or more.

[Non-aqueous electrolyte]
The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The nonaqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolyte solution), and may be a solid electrolyte using a gel polymer or the like. Examples of non-aqueous solvents that can be used include esters, ethers, nitriles (acetonitrile, etc.), amides (dimethylformamide, etc.), and a mixture of two or more of these.

  Examples of the esters include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, and the like. Examples thereof include carboxylic acid esters such as chain carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone.

  Examples of the ethers include cyclic ethers such as 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, furan, and 1,8-cineol. , 2-dimethoxyethane, ethyl vinyl ether, ethyl phenyl ether, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, triethylene glycol Examples include chain ethers such as dimethyl ether.

  As the non-aqueous solvent, it is preferable to use at least a cyclic carbonate among the solvents exemplified above, and it is more preferable to use a cyclic carbonate and a chain carbonate in combination. Moreover, you may use the halogen substituted body which substituted hydrogen of various solvents with halogen atoms, such as a fluorine, as a non-aqueous solvent. The non-aqueous solvent preferably contains vinylene carbonate or fluoroethylene carbonate.

The electrolyte salt is preferably a lithium salt. Examples of lithium salts include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₅ ) ₂ , LiPF _6-x (C _n F _{2n + 1} ) _x (1 <x < 6, n is 1 or 2). These lithium salts may be used alone or in combination of two or more. The concentration of the lithium salt is preferably 0.8 to 1.8 mol per liter of the nonaqueous solvent.

[Separator]
As the separator, a porous sheet having ion permeability and insulating properties is used. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. As the material of the separator, polyolefin such as polyethylene and polypropylene is suitable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to these Examples.

<Experiment 1>
[Production of positive electrode]
Lithium cobaltate, acetylene black, and polyvinylidene fluoride were mixed at a mass ratio of 95: 2.5: 2.5 and added to N-methyl-pyrrolidone (NMP). This was stirred using a mixer (manufactured by Primics, TK Hibismix) to prepare a slurry for forming a positive electrode mixture layer. The slurry was applied to both surfaces of an aluminum foil, dried at 105 ° C. in the air, and rolled to produce a positive electrode. The packing density of the positive electrode mixture layer was 3.6 g / ml.

[Production of negative electrode]
SiO _x (x = 0.93,) having an average primary particle size of 5.0 μm is prepared, methane is used on the surface, and the carbon coverage on the SiO _x surface is 5% by the thermal CVD method. The film was formed as follows. And the SiO _x, and graphite, was a mixture so 5:95 by mass ratio as the negative electrode active material. This negative electrode active material, carboxymethylcellulose (CMC, manufactured by Daicel Finechem, # 1380, degree of etherification: 1.0 to 1.5), and SBR were 97.5: 1.0: 1. 5 was added, and water as a diluent solvent was added. This was stirred using a mixer (manufactured by Primics, TK Hibismix) to prepare a slurry for forming a negative electrode mixture layer. The slurry was applied on both sides of a copper foil, dried at 105 ° C. in the atmosphere, and rolled to prepare a negative electrode. The packing density of the negative electrode mixture layer was 1.60 g / ml.

[Preparation of non-aqueous electrolyte]
Lithium hexafluorophosphate LiPF ₆ was added to a mixed solvent mixed so that ethylene carbonate (EC): diethyl carbonate (DEC) = 3: 7 (volume ratio) to 1.0 mol / liter. Thus, a non-aqueous electrolyte was prepared.

[Production of Battery C1]
A tab was attached to each of the electrodes, and the positive electrode and the negative electrode were wound in a spiral shape through a separator so that the tab was positioned on the outermost periphery, thereby preparing a wound electrode body. The electrode body is inserted into an exterior body made of an aluminum laminate sheet and vacuum-dried at 105 ° C. for 2 hours, and then the non-aqueous electrolyte is injected, and the opening of the exterior body is sealed to form the battery C1. Produced. The design capacity of the battery C1 is 800 mAh.

<Experiment 2>
Except that SiO _x (x = 0.93) with an average primary particle diameter of 1.0 μm was used and the film was formed so that the carbon coverage on the SiO _x surface was 50%, the same method as in Experiment 1 was used. A battery C2 was produced.

<Experiment 3>
By adding coal pitch of 10 wt% with respect to SiO _x, except for two hours at 800 ° C., by performing heat treatment, the carbon coverage for SiO _x surface is formed so as to be 50%, Experiment 1 A battery C3 was produced in the same manner as described above.

<Experiment 4>
A battery C4 was produced in the same manner as in Experiment 1 except that the film was formed so that the carbon coverage with respect to the SiO _x surface was 50%.

<Experiment 5>
A battery was prepared in the same manner as in Experiment 1 except that SiO _x (x = 0.93) having an average primary particle diameter of 20 μm was used and the carbon coverage on the SiO _x surface was 50%. C5 was produced.

<Experiment 6>
A battery C6 was produced in the same manner as in Experiment 1 except that the film was formed so that the carbon coverage with respect to the SiO _x surface was 80%.

<Experiment 7>
A battery R1 was produced in the same manner as in Experiment 1 except that the SiO _x surface was not coated with carbon.

<Experiment 8>
A battery R2 was produced in the same manner as in Experiment 1 except that the film was formed so that the carbon coverage on the SiO _x surface was 100%.

<Experiment 9>
Except that SiO _x (x = 0.93,) with an average primary particle size of 1.0 μm was used and the film was formed so that the carbon coverage on the SiO _x surface was 100%, the same method as in Experiment 1 was used. A battery R3 was produced.

<Experiment 10>
A battery was prepared in the same manner as in Experiment 1 except that SiO _x (x = 0.93) having an average primary particle diameter of 20 μm was used and the carbon coverage on the SiO _x surface was 100%. R4 was produced.

<Battery performance evaluation>
The batteries C1 to C6 and R1 to R4 were evaluated for cycle characteristics and are shown in Table 1.

[Cycle test]
Charging: Constant current charging was performed at a current of 1.0 It until the voltage reached 4.2 V, and then constant voltage charging was performed at a voltage of 4.2 V until reaching a current of 0.05 It.
Discharge: Constant current discharge was performed until the voltage reached 2.75 V at a current of 1.0 It.
-Rest: The rest time between the charge and the discharge was 10 minutes.
The number of cycles to reach 80% of the discharge capacity at the first cycle was measured and defined as the cycle life. The cycle life is an index with the cycle life of the battery C4 as 100.

<Z _a and z _a / R>
Under an inert atmosphere, the battery was disassembled after 25 cycles and after 100 cycles, the negative electrode was cut by ion milling apparatus, while observing the cut surface with SEM, it performs a composition analysis using EDS, SiO _x The O / Si ratio (x _s ) near the surface and the O / Si ratio (x _b ) near the center are measured, and the distance from the surface of the point where x = (x _s + x _b ) / 2 is determined as z _a ( μm). The average particle size measured by a laser diffraction scattering method (D ₅₀₎ and R ([mu] m), and calculates the value of z _a / R. Moreover, the cross-sectional SEM image of the negative electrode of battery C4 was shown in FIG.

As can be seen from Table 1, the batteries C1 to C6 that satisfy z _a / R of 0.025 to 0.4 have improved cycle life compared to R1 to R4. The cycle life of the battery C4 was 250 cycles.

The oxygen concentration of the surface layer of SiO _x (after 25 cycles) used in batteries C1 to C6 was higher than the oxygen concentration (uniform concentration in particles) of SiO _x (after 25 cycles) used in batteries R2 to R4. That is, it is considered that the surface layer of SiO _x (after 25 cycles) used in the batteries C1 to C6 had less active Si than the surface of SiO _x (after 25 cycles) used in the batteries R2 to R4. It is considered that the cycle life of the batteries C1 to C6 is improved because the reaction between the active Si on the surface of the SiO _x and the electrolytic solution is less likely to occur and the side reaction product is less likely to be deposited.

It was confirmed by Auger electron spectroscopy that a lithium silicate phase was present in the surface layer of SiO _x (after 25 cycles) used in the batteries C1 to C6. By lithium silicate phase is formed on the surface layer of SiO _x, reaction of the SiO _x and the electrolytic solution is further suppressed, that side reaction products become less likely to further deposition cycle life of the battery C1~C6 Is thought to have improved.

The oxygen concentration of the surface layer of SiO _x (after 25 cycles) used in batteries C1 to C6 was lower than the oxygen concentration of the surface layer of SiO _x (after 25 cycles) used in battery R1. That is, it is considered that the surface layer of SiO _x (after 25 cycles) used in the batteries C1 to C6 contained more active Si than the surface of SiO _x (after 25 cycles) used in the battery R1. Nevertheless, the cycle life of the battery R1 is significantly lower than that of the batteries C1 to C6 because the oxidation of Si proceeds too much on the surface of the SiO _x , resulting in a decrease in capacity of the active material itself as the cycle progresses. It is thought that it was because it happened.

In addition, the SiO _x after 100 cycles used in the batteries C1, C2, and C6 tended to have both z _a and R larger than the SiO _x after 25 cycles, but the value of z _a / R was It has hardly changed.

  Although the cycle tests of the batteries C1 to C6 and R1 to R4 were performed under the above-described conditions, it is considered that the same results as in Table 1 can be obtained if the charge / discharge conditions of the generally known cycle test are used. That is, if the constant current value during charging / discharging is 0.2 It to 20 It, the charge end voltage is 4.2 to 4.7 V, and the discharge end voltage is 2.0 to 3.1 V, the result equivalent to Table 1 is obtained. It is thought that it is obtained.

<Experiment 11>
A battery C7 was produced in the same manner as in Experiment 1, except that the carbon coverage on the SiO _x surface was 50% and that 2% by weight of vinylene carbonate was added to the non-aqueous electrolyte.

<Experiment 12>
A battery C8 was produced in the same manner as in Experiment 1, except that the carbon coverage on the SiO _x surface was 50% and that 2% by mass of fluoroethylene carbonate was added to the non-aqueous electrolyte.

<Battery performance evaluation>
The battery C7 and C8 were subjected to the above cycle characteristic evaluation and are shown in Table 2.

As can be seen from Table 2, when the electrolytic solution contains vinylene carbonate or fluoroethylene carbonate, the cycle life is improved. By dense film on SiO _x is formed on the surface of the reaction and with the surface of the SiO _x and the electrolyte, the reaction between the carbon and the electrolyte covering the SiO _x surface is suppressed, and generation of side reaction products This is thought to be due to the suppression of deposition.

Claims (4)

A nonaqueous electrolyte secondary battery comprising a negative electrode active material containing a material represented by a general formula SiO _x (0 <x <2),
When the value of x in the general formula is x _s at the surface of the substance and x _b at the center of the substance, x _b <x _s and x = (x _s + x _b ) / in the substance When the depth from the outermost surface to be 2 is z _a (μm) and the average particle diameter of the substance is R (μm), 0.05 <z _a , 0.025 ≦ z _a /R≦0.4 , R ≦ 30 , a non-aqueous electrolyte secondary battery.
The surface of the substance is coated with an electronically conductive material;
The coverage of the electronic conductive material on the surface of the substance is less than 100%,
The non-aqueous electrolyte secondary battery according to claim 1, wherein the electronic conductive material is attached to a surface of the substance.   The nonaqueous electrolyte secondary battery according to claim 2, wherein a coverage of the electronic conductive material on a surface of the substance is 5% to 80%. The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein a region from _a surface of the substance to za includes _a lithium silicate phase.

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